Gauging device



Feb. 27, 1945. I J, STRAW 2,370,503

GGGGGGGGGGG CE ate with the threads on the workpiece.

Patented Feb. 27, 1945 Jesse H.- Straw, Dayton, Ohio, assignor to The Shefiield Corporation, Dayton, Ohio, a corporation of Qhio Applicationseptember This invention relates to gauges and more particularly to thread gauges.

One object of the invention is the provision of a thread gauge so arranged and constructed as to readily determine the concentricityof a screw thread with respect to some other'portion of the piece on which the thread is provided.

Another object'is the provision of a gauging member having a threaded portion adapted for snug threaded engagement with the screw thread of a workpiece and also having reference means ,whereby the longitudinal axis of the thread member is located, the threads of said member having a lead which is slightly different from the lead of the threads on the workpiece.

Other objects and advantages of the invention will be apparent from the following description, the appended claims and the accompanying drawing, in which,

Fig. 1 is a side elevation, partly in section,

13, 1943, Serial No. 502,129

less thanthe pitch diameter of the threads on the workpiece, so that a tight fit between these threads is obtained only on opposite sides of spaced threads of the plug after several of the threads are engaged. The difference in pitch is only a small fractional part of the distance between adjacent threads on the plug so that a suitable number of threads of the plug will enter the threads of the workpiece, and the degree to which the gauging member enters before a tight fit is obtained depends upon the amount of variation in thread spacing on the workpiecethreads from a normal or intended thread pitch. Thus if the threads on the workpiece are expected or intended to have a thread spacing of some standard value whereas as a matter of fact the parshowing a portion of 'a thread gaugeembodying the present invention and illustrating its association with a threaded part the concentricity of which is to be determined;'

Fig. 2 is a central vertical section through the ticular workpiece gauged has a slightly greater threadspacing, orlead, the threaded plug II will not enter quite as'far as it would if the threads were of standard spacing. The length of the thread on the plug is sufiicient, however, to insure a tightor a snug fit between the threaded plugand the workpiece even if the pitch spacing gauging device and the workpiece associated with it; and

Fig. 3 is an enlarged sectional view showing how the threads on the gauging member cooper- Referring more particularly to the drawing, in which the same reference numerals have been applied to like parts in the several views, It! generally designates a workpiece having a threaded portion the concentricity, of which should be accurately determined withrespect to some other portion of the workpiece. l l designates a threaded gauging member employed in accordance with the present invention to accurately determine the concentricity of the threads on the workpiece. For purposes of illustration of one embodiment of the invention, the workpiece is provided with an internal thread 12 and an external thread l3, while the gauging device employed in conjunction with these threads comprises a threaded plug II which cooperates with the threads [2 and a threaded'ring l5 which cooperates with the threads I3. The plug II is provided with external threads l3 which are substantially uniform in pitch diameter and in lead but which have a lead slightly difierent from the lead of the threads l2. As shown, the lead of the threads I6 is slightly less than the standard thread spacing of the internal threads on the workpiece, and the pitch diameter of the threads l8 is also slightly of the threads on the workpiece is a permissible amount less than the true or intended pitch.

As will be apparent, since the thread lead on the gaugingplug does not correspond with the true or intended thread lead on the workpiece, the two parts may be threaded together very readily and will have a firm or snug connection avoiding any possible play or misalignment with respect to one another. The plug II is provided with some means or reference surface which is exactly concentric with the threads on the plug," and as shown, this means is afforded by an annular surface l1, accurately made so as to be truly concentric with the threads it. Thus by measuring the eccentricity of the cylindrical surface l'l any indications or readings so obtained represent the amount of eccentricity of the threads l2 with respect to some other surface on the workpiece. By rotating the workpiece and the gauging plug about an axis, with a work contacting plunger l8 of a suitable indicating gauge bearing against the surface I1, the pointer on the gauge, if it maintains a stationary position, will show that the axis about which the workpiece is rotated is truly concentric with the threads 12 on the workpiece.

The workpiece may be rotatably held by means on an arbor 20 arranged between centers 2| and 22 so that the arbor can be readily turned about its own longitudinal axis by the person making the test. The arbor fits in a cylindrical passage 23 of the workpiece with no play existing between these parts. As the workpiece and the threaded plug II are rotated, the gauge operated by the work contacting plunger I8 will give an indication v or the concentricity of the threads l2 with respect to the passage 23, any variation of the gauging plunger from a normal position showing the amount of eccentricity that exists between the axesof the threads 12 and thesurface to be compared with'it.

The threads I2 may be compared with some other threaded portion of the workpiece such as the threads Hi to determine whether the threaded portions l2 and 13 are truly concentric with one another or to determine the amount or eccentricity that may be present. For this purpose a gauging member I5, in the form of a threaded ring having threads the lead of whichis slightly difierent from that of the threads l3, and having I a pitch diameter slightly in excess of the pitch diameter of threads I3 ,is adapted to be screwed will ac urately show the degree of eccentricity of v th threads IS with respect to the center aboutwhich the. work iece is revolved. By comparing the readings of the two gauges operated by the two gauging plungers lBand. the exactamount of eccentricity ofthe two threaded porticns of the workpiece may be accurately determined.

A will now be apparent the gauging member or members employed with the workpiece are provided with threads that may be readily thread.- ed into or on the workpiece'witha very free running fit .until opposite sides of the threads of any threaded portion come up tightly into engagement and prevent all play with respe t to. the innerconnected portions. The indicating gauze or gauges employed in conjunction with the per-- tions of the workpiece to. be compared bear against a cylindrical surface or surfaces so that ny suitable auging or indicating device can .be used.

While the form of apparatus herein described constitutes. a preferred embodiment of the inven, tion, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

V 1. Gauging means for use in determining the concentricity of a. screw thread of a workpiece with respect to. a different portion of the workpiece, comprising a threaded member adapted for snug threaded engagement with the said screw thread and having reference means definitely locating the longitudinal axis of said member, the V threaded part of said member having threads of substantially uniform diameter the lead of which "is slightly different from the standard lead of the threads on the workpiece.

2. Gauging means for determining the concentricity of a screw thread of a workpiece with respect to a different portion of the workpiece comprising a threaded plug adapted for threaded engagement with the said screw thread and having threads. only on opposing jsidesof spaced threads of the plu 3. A gauging plug for use in determining-concentricity of a straightscrew thread of a work piece comprising a threadedfplug adapted for threaded engagement with aid screw thread and having an annular surface beyond the thread on the plug which is exactly concentric with the plug thread, the threaded part of said plug having straight threads slightly smaller in pitch diameter than the threads of the workpiece and with a lead which is slightly different from the lead of thethreads of the workpiece. i

4. A gauging ring for use in determining concentricity of a straight screw thread of a workpiece, said ring having 'internal threads of'substantially uniform diameter the lead of which is slightly different from the standard lead of the threads on the workpiece to provide snug engagement with the workpiece threads only on opposing Sides of spaced threads of the ring, said ring having a reference surfacedefinitely locating the longitudinal axis of its internal threads.

JESSE H. S'I'RAW. 

